[Imported] Multi-Master Sync avoids interference between co-located Access Points

[sbeadle]

>>Message imported from previous forum - Category:Trio Data Radios<<
User: joelw, originally posted: 2018-10-17 18:49:08 Id:81
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.

-------------------------------

**_jweder:
The procedure below summarizes how to configure two or more Trio J Series Access Points or K Series Masters to co-exist without causing interference to each other. Without this feature the antennas would need to be one directly above the other spaced by about 4 metres. (13.5 feet) With this feature, the two radios may be mounted at the same level, just a metre or so apart._**

________________________

- Open the cover of both Access Point (Master) radios with a 2.5 mm hex driver.
- Move the X11 jumper from the default RSSI position to the MSync position
- Replace the cover, ensuring the case is properly sealed and the screw is tight
- Make a cable with DE9 male on both ends that connects pin 9 on both ends together
- If there are more than two Access Points (Masters) the cable must be made in a "daisy-chain" fashion. The signal is not RS-232 so several devices may be connected.
- Both radios should have a common power supply, thus already have a common ground. But pin 5 on both ends could also be included.
- Configure both radios as Access Points (Masters), but ensure they have different downstream Network ID's
- Set Hopping Interval the same in both radios otherwise they won't be able to stay in sync with one another.
- Configure one radio's General Purpose I/O pin (in the Radio Advanced section in J Series, or in the Port B Advanced section in K Series) to act as the MultiMaster Primary
- Configure the second radio's GPIO pin so this radio (and any others if more than 2 AP's share the location) is a MultiMaster Secondary
- Set other Access Point radio configuration parameters as required for each network.

Once these changes are made the Access Points will both have the first half of each hop to Transmit. During the second half both will switch to Receive. In this way neither can interfere with the other.

**If it is also desired to share the same antenna** due to space constraints a power combiner/splitter such as the Mini-Circuits ZAPD-1-N+ may be used for 900 MHz, or the ZAPD-4-N+ for 2.4 GHz. The one concern with any such device is that it will cause about 3.5 dB of loss of transmit power on both radio systems. A higher gain antenna may be used if required.